New optical systems for small-size telescopes

Yu. A. Klevtsov: The deficiencies of the
popular mass-produced telescopes of the Schmidt-Cassegrain
design include their low aperture ratio and narrow spectral
range. The novel systems for Cassegrain telescopes with
a meniscus corrector proposed here are free of these deficiencies.
Two such systems are described: a system with corrector
lenses made from the same material and a system with corrector
lenses made from different materials. The systems are technologically
convenient (all the surfaces are spherical) and are distinguished
by small lens diameters (down to 1/3 of the effective aperture),
compactness, a high aperture ratio (up to 1:6.5-1:7), high-quality
aberration correction, and a broad spectral range (400-900
nm), which is sufficient for working with modern photographic
materials and CCD arrays.More detail: [in English>>]
[in German>>]
[in Russian>>]

Top Ten TALScopes Myths

Bill Brady: 1. TAL mounts are junk.
FALSE. TAL mounts are built the old fashioned way, with massive solid steel
shafts and preloaded ball bearings on the worm and RA shafts. The larger GEM
also has preloaded ball bearings on the Declination shaft. The TAL mounts do
need adjustment, they have no springs or plastic thrust bearing parts to take
up the slack. With periodic adjustment and lubrication, they will last a
lifetime.More detail: [at Yahoo! groups>>]
[at this website>>]

A compact short-focus telescope with spherical optical
surfaces

Robert J. Magee: The optical system consists
of a perforated primary mirror, a two-element corrector
lens (with one surface aluminized to function as the secondary
mirror), a diagonal mirror and the eyepiece. The small two-element
corrector lens replaces the full-aperture lens of the popular
Maksutov system. The combination of an achromatic lens and
a second-surface mirror that I use is known as a Mangin
mirror. [More detail>>]

Maksutovs with Subaperture Correctors

Australian amateur Ralph W. Field, after completing the
design calculations presented in this article, begins to
grind the small meniscus corrector for a working telescope.
[More detail>>]

A Telescope-Making Tradition in Russia

Sergey Maslikov: The first Russian-made astronomical
optic was probably crafted by Jacob Bryus, a member
of Peter the Great's inner circle, who fashioned a concave
mirror for a reflecting telescope in 1733. But our country's
first true amateur telescope maker was Ivan Kulibin.
A self-educated mechanic from Nizhny Novgorod, Kulibin managed
to get his hands on a Gregorian reflector in 1767. He was
able to determine the formula of its speculum-metal mirror
- a hard, brittle alloy of copper and tin - and he proceeded
to build a machine for grinding and polishing mirrors and
lenses. Kulibin also crafted flint glass for making achromatic
objective lenses. [More detail>>]